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Plant materials for water gardens should be cleaned and inspected to be sure they are not harboring invasive aquatic plants or aquatic insects.

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Popularity of water gardening poses invasive species threat

April 18, 2013

Popularity of water gardening poses invasive species threat

UNIVERSITY PARK, Pa. -- When you look at lovely water gardens in backyards and at businesses -- and feel soothed by the serenity they convey -- you would not guess that they represent troubled waters for ecosystems in the mid-Atlantic region.

But they can, and the threat water gardens present is becoming increasingly serious simply because they are so popular, according to an expert in Penn State's College of Agricultural Sciences.

The explosion in popularity of water gardening has contributed to the proliferation of aquatic invasive species, according to Diane Oleson, a Penn State Extension educator based in York County, who created an educational program that shows water gardeners how to avoid giving aquatic invaders a free ride.

Water gardening is one of the fastest growing branches of the aquarium trade, she noted. A 2010 survey by the American Society of Landscape Architects reported nearly 88 percent of clients were interested in fountains or ornamental water features.

“Because water gardening is so popular and Pennsylvania’s watersheds are so extensive, water gardeners must be careful not to inadvertently introduce aquatic invasive plants and animals into our rivers and streams," Oleson said. "The risk can be minimized through proper selection, handling and disposal of plant and animal materials.”

Invasive aquatic species with common names such as water chestnut, yellow flag Iris, hydrilla, water lettuce, yellow floating heart, zebra mussels, and Japanese and Chinese mystery snails -- just to name a few -- can cause major problems if they escape from a water garden and become established in a nearby lake or stream.

Invasive plants tend to displace native plants over time and create an unhealthy ecosystem because a lot of them form huge, dense, one-species stands in which other plants can't grow. "Animals don't eat them because the species that would control them are back in Asia or Europe or wherever they came from," Oleson explained.

"The way that these things spread around is flooding -- if you have a lot of rain they can escape from a water garden and get into a storm sewer or stream and eventually into rivers and lakes. So, there is a tremendous potential for invasives to be washed out of essentially an open bowl in your yard and into the wild.

"These plants do have hardiness zones -- places where they are supposed to grow and survive -- but it turns out that invasive plants just don't read the books."

Oleson and her team created a PowerPoint presentation with a script, related handouts on invasive species and water gardens, and a short video demonstrating techniques for cleaning and inspecting water-gardening materials. The presentation is tailored to the mid-Atlantic region and is available to natural-resource educators.

She hopes the materials Penn State Extension provides for use in public outreach efforts will empower educated audiences to make wiser choices about plant and animal materials to be used in water gardens.

"I have created a train-the-trainer presentation so that someone could absorb the presentation, and with some background information and support materials on hand, they could present it to interested groups, such as conservation districts, garden clubs or lake or watershed associations," she said.

"This is a tool that can be used by anyone," Oleson added. "It really was designed to be used by people who have an interest in invasive species and water gardening and want to educate others. We highlight the appropriate controls and disposal techniques to avoid unintended introductions."

The presentation, companion materials and video are available on Penn State Extension's Water Resources website under Pond Management.